Research On The Mechanism And Control Strategy Of Magnetorheological Elastomer Mount For Powertrains

With the increase of the engine power and the improvement of automobile-lightweight level,the influence of the vibration of powertrain on NVH(Noise,Vibration and Harshness)performance of automobiles is increasingly evident.In order to isolate the vibration transmitting from powertrain to body,engine mounts are installed between powertrain and body.However,the mechanical parameters of traditional passive mounts cannot be adjusted with the working conditions of powertrains,and it is very difficult to effectively achieve isolation performance in a wider operation frequency range.Magnetorheological elastomers(MREs),as one kind of smart materials,have the advantages of continuously controlled stiffness,rapidly response time and good reversibility,and exhibit good application prospects in the field of powertrain vibration attenuation.In this dissertation,MREs are applied for the vibration attenuation in powertrain mount system.For the vibration characteristics of powertrain mount systems and the own working characteristics of MREs,the studies on the modeling of viscoelasticity of MREs,the design of a semi-active mount structure,the design of a semiactive control algorithm and the experimental verifications are conducted.The goal of the vibration attenuation for powertrain mount systems with the application of MREs is elementarily realized.The major researches in this dissertation are summarized as follows:1.The principle of an amplitude-,frequency-,and magneto-dependent linear dynamic viscoelastic model for isotropic MREs is proposed and investigated.The viscoelasticity of MREs is divided into amplitude-and frequency-dependent mechanical viscoelasticity and amplitude-,frequency-,and magneto-dependent magnetic viscoelasticity.Based on the microstructures of MREs and magneto-elastic theory,the mathematical expressions corresponding to the mechanical viscoelasticity and magnetic viscoelasticity are derived,respectively.The dynamic characteristics of a fabricated isotropic MRE sample under different strain amplitudes,excitation frequencies and external magnetic fields are tested,and the parameters of the proposed model are identified correspondingly.The loss factors of the MRE sample under different loading conditions are analyzed and compared with the test results to evaluate the effectiveness of the proposed model.2.The principle and the structure of a novel MRE dynamic vibration absorber(DVA)for powertrain mount systems of automobiles is proposed,designed and realized.The MRE DVA consists of a vibration absorbing unit and a passive vibration isolation unit,the vibration absorbing unit is utilized to absorb the vibration energy and the passive vibration isolation unit is used to support the powertrain.The optimal parameters of the electromagnetic circuit of the MRE DVA are calculated based on Kirchoff's law,and the finite element method is employed to validate the electromagnetic circuit of the MRE DVA.The theoretical frequency-shift principle is analyzed via the established constitutive equations of the circular cylindrical MRE.The prototype of the MRE DVA is manufactured to verify its frequency-shift property.3.The vibration characteristics of the powertrain mount system based on the MRE DVA is analyzed and tested.The proposed MRE DVA is employed in a powertrain mount system to replace the conventional passive mount,and the vibration model of the powertrain mount system installed with the MRE DVA is established,and its vibration characteristics are analyzed correspondingly.A test rig of the semi-active powertrain mount system based on the MRE DVA is built to validate the vibration attenuation performance of the manufactured MRE DVA.4.A rapid,stable,and effective control algorithm for MRE DVA applied to automobile powertrain mount systems is proposed and validated.According to the principle of system reconfiguration,a full state observation model using an adaptive Kalman filter with SageHusa noise estimator is developed.With the state vectors estimated by the Kalman filter,the phase difference between the displacement of the dynamic mass of the MRE DVA relative to the powertrain and the absolute displacement of the powertrain is updated continuously.By adjusting the applied current to the MRE DVA with fuzzy logic rules corresponding to the cosine value of the phase difference,the natural frequency of the MRE DVA could track the excitation frequency of the powertrain well,which results in vibration attenuation of the powertrain mount system.To verify the effectiveness and the stability of the proposed algorithm,with consideration of excitation noise,time delays and parametric uncertainties,the simulation results of vibration attenuation performance of the MRE DVA for the powertrain mount systems when under time-varying excitation is carried out.Besides,a test rig for the vibration attenuation of semi-active powertrain mount system is built to validate the vibration control effect of the proposed algorithm.The proposed viscoelastic model for isotropic MREs can describe the relationships of the mechanical property of MREs with strain amplitudes,excitation frequencies and external magnetic fields.The proposed model can be applied to design the MRE based structures and to analyze its mechanical behavior in engineering applications.Meanwhile,the designed MRE DVA prototype and the proposed semi-active control algorithm can provide a new way to solve the vibration problem of powertrain mount systems,and have some reference meaning for the future studies.